Abstrak
This study examines the effect of Content and Language Integrated Learning (CLIL) on students' vocabulary mastery and critical thinking skills at SMAN 4 Bukittinggi. Vocabulary and critical thinking are fundamental to literacy and academic success, enabling students to engage with texts and analyze, evaluate, and create new understandings. Despite their importance, many educational systems, especially in non-native English-speaking contexts, struggle to integrate language learning with cognitive skill development. This research employs a quasi-experimental design involving 98 eleventh-grade students, divided into an experimental group receiving CLIL instruction and a control group receiving traditional instruction. Data collection includes pre-tests and post-tests to assess vocabulary and critical thinking, analyzed using Multivariate Analysis of Variance (MANOVA). The results indicate significant improvements in both vocabulary mastery (F_count = 3467.035, p 0.05) and critical thinking (F_count = 7.403, p 0.05) among students taught using the CLIL approach. These findings suggest that CLIL effectively enhances vocabulary and critical thinking skills, making it a valuable addition to language education curricula